Low-emissivity glass refers to glass onto which a low-emissivity layer containing a metal having high reflectivity in an infrared region, such as silver (Ag), is deposited as a thin film. Such a low-emissivity glass is a functional material that reflects solar radiation in summer and conserves infrared light generated from an indoor heater in winter, thereby providing an energy-saving effect of buildings. Techniques related to low-emissivity glass are disclosed in various documents including Korean Patent Laid-open Publication No. 10-2010-0021355 and the like.
In general, silver (Ag) used for a low-emissivity layer is highly susceptible to oxidation, and thus, dielectric layers are deposited as antioxidant layers on top and bottom surfaces of the low-emissivity layer. In addition, such dielectric layers serve to increase transmittance of visible light.
A typical dielectric layer includes a metal oxide, for example, oxides of zinc (Zn), titanium (Ti), tin (Sn), and the like, or a complex metal (SnZn) of zinc and tin. However, the metal oxide for the dielectric layer is likely to cause interfacial reaction between the oxide and an adjacent metal layer after heat treatment, whereby transmittance of visible light can be easily varied before and after heat treatment.